Apparatus for the introduction of volatile additives into a melt

ABSTRACT

Introduction of vaporizable additives, such as magnesium, into an iron melt in which the vaporization is initiated by a tilting movement of a treatment vessel. The vaporizable material is contained in a separate compartment which can be externally charged and which, in one position of the vessel segregates the additive from the melt, but on tilting the vessel, permits communication with the melt through openings located at different levels. The vapor bubbles formed ascend through the melt with such a size and in such a number that at least a portion of the bubbles escape from the surface of the melt. The vapor bubbles have a great surface area to provide, for example with magnesium, a yield of at least 30 percent and preferably more than 40 percent of the additive in the melt while the velocity of the ascending vapor bubbles is such as to produce a flushing action on the melt resulting in a reduction of the reaction products and residual undesirable impurities in the melt.

[54] APPARATUS FOR THE INTRODUCTION OF VOLATILE ADDITIVES INTO A MELTInventor:

Anton Alt, Mettmann, Germany Georg Fischer Aktiengesellschaft,Schaffhausen, Switzerland Filed: Dec. 15, 1971 Appl. No.: 208,074

Assignee:

Related US. Application Data Division of Ser. No. 793,065, Jan. 22,1969, Pat. No. 3,666,449.

[30] Foreign Application Priority Data Jan. 26, 1968 Dec. 3, 1968Switzerland 1274/68 Switzerland ..l796l/68 US. Cl. ..266/34 T, 266/39Int. Cl ..C2lc 7/00 Field of Search... ..266/34 A, 34 T; 75/130 R Reierences Cited UNITED s'n TEs PATENTS 2,698,749 1/1955 Fisliell ..266/34T[451 Apr. 3, 1973 Primary Examiner-Gerald A. Dost AttorneyWerner W.Kleeman [57] ABSTRACT Introduction of vaporizable additives, such asmagnesium, into an iron melt in which the vaporization is initiated by atilting movement of a treatment vessel. The vaporizable material iscontained in a separate compartment which can be externally charged andwhich, in one position of the vessel segregates the additive from themelt, but on tilting the vessel, permits communication with the meltthrough openings located at difierent levels. The vapor bubbles formedascend through the melt with such a size and in such a number that atleast a portion of the bubbles escape from the surface of themelt. Thevapor bubbles have a great surface area to provide, for example withmagnesium, a yield of at least 30 percent and preferably more than 40percent of the additive in the melt while the velocity of the ascendingvapor bubbles is such as to produce a flushing action on the meltresulting in a reduction of the reaction products and residualundesirable impurities in the melt.

15 Claims, 2 Drawing Figures APPARATUS FOR THE INTRODUCTION OF VOLATILEADDITIVES INTO A MELT CROSS-REFERENCE TO RELATED CASE The presentapplication is a divisional and continuation-in-part application of mycommonly assigned, copending U.S. application, Ser. No. 793,065, filedJan. 22, 1969, and now U.S. Pat. No. 3,666,449 and entitledz: METHOD FORTHE INTRODUCTION OF VOLATILE ADDITIVES INTO A MELT.

BACKGROUND OF THE INVENTION The present invention relates to a new andimproved apparatus. for the introduction of volatile or vaporizableadditives into a melt, especially magnesium, into a iron-carbon melt, inwhich the vaporization is initiated by a tilting movement of a treatmentvessel whereby the volatile additives are immersed beneath the surfaceof the melt, and further, wherein the speed of vaporization is retardedby means of a receiving compartment for the additives which are to bevaporized, such receiving compartment being equipped with openingsdirected into the interior of the treatment vessel and relates furtherto the use of the same for the production of various materials.

The introduction of magnesium into iron melts is the surest technicaland the most economical manner to produce iron-carbon cast materialswith spherical graphite. In so doing, magnesium, as well as also otherelements of the earth alkaline group and the group of the rare earths,causes, in known manner, a separation of the graphite in spherical formduring solidification and/or subsequent heat treatment, and thereforeresults in improved mechanical properties.

However, the introduction of magnesium is associated with knowndifficulties. Its specific weight of 1.74 g/cm is considerably lowerthan that of the iron melts. Above all, magnesium, with a boiling pointof ll07C at a generally encountered temperature of the iron melt ofl480C, develops a vapor pressure of approximately 12 atmospheres.Therefore, in the majority of instances, magnesium is introduced in theform of key alloys or hardeners with a magnesium content of to 30percent into the melt which is to be treated, since the vapor pressureis reduced in accordance with the dilution.

However, the use of key alloys or hardeners possesses the drawback thatother elements are introduced into the melt to a certain degree inundesirable quantities. Consequently, the possibility of using such keyalloys or hardeners is generally limited. The use of such materialsnecessitates starting with melts of low sulfur content. Melts of lowsulfur content can ordinarily only be realized in a basic meltingfurnace unit or in an acidic melting furnace unit while using asulfur-poor material charge or by using a special desulfurizingtechnique. Moreover, the use of key alloys or hardeners is associatedwith increased costs. Thus, the cost for the same quantity of addedmagnesium utilizing conventional key alloys or hardeners amounts toabout five to twenty times that of using pure magnesi- Accordingly, awhole series of techniques have become known to the art which areconcerned with the introduction of pure magnesium into the iron melts.Thus, at the present time, a small quantity of cast iron with sphericalgraphite may be produced according to a technique in which puremagnesium is added under a pressure which corresponds to the vaporpressure at the given treatment temperature. Methods are also known tothe art wherein pure magnesium is continuously added in solid, liquid,or gaseous condition, the speed of reaction being controlled by thespeed with which the material is added. It has also already beenproposed to reduce to an acceptable degree the vigor or intensity of thereaction of magnesium during continuous or one-time addition by mixingthe same with suitable inert materials in powderyor pasty-likecondition, by imbuing porous materials with magnesium, by the use ofsuitable coatings, or by introducing the magnesium into a containerhaving predetermined openings limiting the contact with the melt.

In addition to the conventional methods of adding magnesium to the meltby pouring-over, immersionor introduction with a pipe or similar device,it has also been proposed heretofore to bring about the addition orintroduction in such a manner that the magnesium is placed into atiltable vessel within a specially provided pocket therefor. Afterfilling with iron the magnesium is brought below the surface of the bathby carrying out a tilting movement through about'90. Additionally, atechnique has also become known according to which the device providedfor the reception of the magnesium is constructed in the form of acompartment which can be externally charged and which is equipped withan opening towards the inside, the size of which is decisive for theheat delivered by convection to the magnesium through the melt and,therefore, for the speed of vaporization. The drawback of this methodresides in the fact that the considerable quantity of vapor hinders thecontinuous flow of heat-supplying melt. Consequently, on the one hand,this causes an irregular reaction process which is associated withviolent eruptions and, on the other hand, the dimensioning of theopening towards the lower extreme is limited and thus renders impossiblea delay or retardation of the reaction to the desired degree.

According to another known method, the yield is considerably increaseddue to the arrangement of a number of small openings, whereby the meltdoes not enter into the chamber or compartment containing the magnesium,rather the heat required for vaporization is delivered by conductingheat through the walls of the chamber. However, with this technique, theflushing effect is practically lost.

SUMMARY OF THE INVENTION Therefore, it is a primary object of thisinvention to provide a new and improved means for the introduction ofvaporizable materials into an iron melt which is free from the foregoingand other such disadvantages.

It is a further object of this invention to provide an apparatus for theaddition of vaporizable materials in a melt, specifically magnesium,wherein the vapor bubbles of the vaporizing additives are permitted toascend through the melt with a size and speed such that there occurs arather extensive absorption of the vapor by the melt and, additionally,the bubbles cause a flushing action which is effective to separate thereaction products between the melt and the vapor.

Another object of this invention is the provision of a tiltable vesselhaving an externally-chargeable compartment for reception of thevaporizable materials which compartment does not communicate with themelt in one position of the vessel, and does communicate with the meltwhen the vessel is tilted by about 90, the compartment having openingsat different levels to facilitate a flow-through of the melt withoutinterference by the vapor bubbles.

A still further object of this invention is the provision of apparatusfor the addition of other materials such as fluxing agents and carbon tothe melt simultaneously with the addition of the vaporizable materials.

The basic objects of the invention are to permit the vapor bubblesformed by the additives to ascend through the melt with such a size andin such a number that at least a portion of the formed vapor bubblesescape from the surface of the bath with such a large velocity that theascending bubbles exert a flushing action upon the melt. This results ina reduction of the reaction products and residual undesirable mixturesor impurities in the melt. n the other hand, the size of the vaporbubbles is chosen to be such that there results a sufficiently greatreaction surface of the vapor bubbles ascending in the melt wherebythere is obtained a favorable yield of the additivesintroduced into themelt, for instance, a magnesium yield in iron-carbon melts at theusualtreatment temperature of at least 30 percent and preferably above40 percent.

In other words, the invention is generally characterized by the factthat the vapor bubbles of the vaporizing additives are permitted toascent through the melt with such a size and in such a number that, onthe one hand, there occurs as extensive as possible absorption orreception of the resulting vapor by the melt and, on the other hand, afavorable flushing action for separating reaction products between themelt and the resulting vapor. During the introduction of the additivesinto the melt, the same can be simultaneously subjected to a circulatorymovement.

As indicated', the invention is concerned with the provision of animproved tiltable treatment vessel for carrying out the aforesaidtreatment technique. This tiltable treatment vessel is manifested by thefeatures that it possesses at least one rigidly mounted receivingcompartment for the additives which compartment can be charged from theoutside, that is externally of the vessel. This receiving compartment isarranged at' least at a portion of the base surface of the interior ofthe ladle or vessel when the vessel is tilted to its treatment orvertically-extending position. Yet, the interior or inner chamber of thereceiving compartment does not communicate with the melt when the vesselis in its filling" or horizontally-extending position. Further, thecompartment includes a number of openings directed towards the interiorof the treatment vessel, which openings are arranged and constructed insuch a fashion thatthe melt passes into the compartment from thetreatment vessel through at least some of the openings when the vesselis in its treatment position to vaporize the vaporizable additives witha certain speed and then passes back through at least some of theopenings from the compartment into the interior or inner chamber of thetreatment vessel.

According to the instant inventive concepts, the techniques hereof maybe used for treating cast iron or malleable cast iron melts which havebeen molten in an acidic process without prior desulfurization, withtechnically pure magnesium or alloys containing large quantities ofmagnesium. Further, these techniques may be used for the production ofcast iron with a carbon content of 2.5 to 3.8 percent carbon, as well'asfor the production of gray cast iron and cast iron with vermiculargraphite.

By virtue of the instant invention, there is simultaneously attained,with an exceptional yield of, for instance, magnesium, such a flushingor agitation effect that the reaction products formed between the meltand the vapor, for instance, magnesium sulfide, are separated from the Imelt. In contrast, with known techniques wherein the melts are treatedwith magnesium, the use of melts having a higher starting sulfur contenthave been excluded due to the formation of undesired inclusions.Consequently, the known treatment of sulfur-rich iron melts, forinstance, cast iron or'malleable cast iron melts from the. acidic cupolafurnace cannot be undertaken without previous desulfurization andwithoutharmful products of reaction remaining in the melt. Sulfur-richstarting melts treated according to the inventive method manifestthemselves, for instance, by a lower content of sulfur remaining in themelt.

As mentioned, it is advantageous, according to this invention, to equipthe receiving compartment or chamber with openings which permit themagnesium vapor bubbles to ascent with such a size or magnitude throughthe melt that the magnesium yield amounts to at least 30 percent andpreferably, more than 40 percent. a

BRIEF DESCRIPTION OF THE DRAWING The invention will be betterunderstood, andobje'cts other than those set forth above will becomeapparent, when consideration is given to the following detaileddescription thereof. Such description makes reference to the annexeddrawing, whereinz- FIG. 1 schematically illustrates an exemplaryembodiment of a tiltable treatment vessel according to this invention inits filling orhorizontally extending position; and

FIG. 2 depicts the tiltable vessel shown in FIG. 1 in its treatment orvertically extending position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawing and, more particularly, to FIG. 1, it will be seen that thetreatment vessel 1 is lined with refractory material and is filled whilein its horizontally extending position with melt 2 to such an extentthat the receiving compartment or'chamber 3, which can be charged fromthe-outside or externally, remains free, that is to say, does notcommunicate with the iron melt 2. After opening the stopperor plug 4,the receiving compartment or chamber 3 is charged with the vaporizableadditive 5 with the addition of possible further additives, as will beexplained hereinafter. By means of the stopper or closure 4, thecharging opening of the receiving chamber or compartment 3 is closed andby means of a suitable cover member 6, the charging opening of thevessel 1 is likewise closed. The cover 6 contains an opening of to 50mm. diameter which is aligned with an opening in the tea can-likepouring spout of the vessel 1 when the cover 6 is in its closed positionto vent the vessel.

After closing the plug 4 and the cover member 6, the entire treatmentvessel 1 can be tilted by a remote controlled drive mechanism (notshown) into the treatment or vertically extending position depicted inFIG. 2. In the vertically extending position of the treatment vessel 1,the receiving compartment 3 is located below the surface of the melt 2,and the melt passes via the apertures or openings 7 and 8 into theinterior of the receiving compartment 3 where it contacts the additive 5causing vaporization of the same. The formed vapor escapes in accordancewith the lift through the discharge openings 8 arranged at the top ofthe receiving compartment 3, while the melt 2 continuously flows throughthe inlet openings 7 arranged at the lower region of the receivingcompartment 3. Accordingly, the delivery of the heat in this mannerassists and supports the vaporization process which is associated with aconsiderable take-up heat. By appropriately dimensioning thecross-section of the openings 7 and 8, it is possible to predeterminethe reaction velocity or speed of the pure magnesium 5 located in thereceiving compartment 3, without requiring undesired additive materials.It is here to be mentioned that the total cross sectional area orcross-section of the compartment openings 7 located at the lower heightor region of the receiving compartment 3 when the-treatment vessel 1 isin its treatment or vertically extending position advantageously may beeither equal to or different from the total cross-sectional area of thecompartment openings 8 located at the upper height or region of suchreceiving compartment. The walls of the compartment 3 are preferablyformed of refractory material, preferably clay graphite plates of 10 to50 mm. thickness. The openings 7 are preferably of a diameter of 20 to40 mm. and the openings 8 are preferably of a diameter of 10 to 30 mm.with the openings 8 distributed over at least a third of the basesurface of the vessel 1 and, in the embodiment under consideration itmay be assumed the entire cross-sectional area of the openings 7 aresmaller than the entire cross-sectional area of the openings 8.

By virtue of the arrangement of the openings 7 and 8 of the receivingcompartment 3 depicted in the drawing, the inlet openings 7 aresubjected to a greater hydrostatic pressure (H than the outlet ordischarge openings 8 (H Due to contact of the molten castiron with themagnesium, there result vapor bubbles which escape through the dischargeopenings '8. Consequently, there exists a through-flow of the moltencast iron through the receiving compartment 3, so that there occurs auniform reaction of the magnesium.

The vapor bubbles escaping through the openings 8 move through the melt2 towards the top and, in so doing, are intentionally taken up in partby the melt. The melt'which is treated in this manner is again emptiedthrough the filling openings by tilting the treatment vessel 1. In orderto dampen the reaction of the pure magnesium located in the receivingcompartment 3, it is possible to additionally introduce into thiscompartment cold scrap iron or another cooling agent. Through thearrangement of one or a number of grid-like intermediate floors formedof refractory material in the vessel 1 (not shown), it is possible tostill further improve the yield of the additives. In order to obtain anoverpressure in the treatment vessel 1, it is possible to appropriatelyconstruct the cover member 6.

The mode of operation of the treatment technique by means of theinventive apparatus will now be explained in conjunction with thefollowing examples:

EXAMPLE 1 A cast iron melt of the following chemical composition:

3 .80 C 1.80 Si 0.57 Mn 0.07 P 0.179% S had added thereto at atemperature of 1500C, according to the inventive process, 0.3 percentpure magnesium in the form of bars, or ingots. The quantity of iron tobe treated amounted to 1700 kg. The vaporization of the magnesium lastedfor seconds. After emptying the treatment vessel into a ladle, thefollowing chemical composition was determined:

0.002 S 0.065 %-Mg Thus, the magnesium yield amounted to 66 percent.

The structure of the cast test pieces after innoculation with 0.5percent ferrosilicon consisted of spherical graphite, that is to say, 96percent Type VI according to VDG Merkblatt, P 441 and 4 percent Type V.

EXAMPLE 2 had added thereto at a temperature of 1510C, according to theinventive process, 0.28 percentpure magnesium in the form of bars, oringots. The amount of iron to be treated amounted to 860 kg. Thevaporization of the magnesium lasted seconds. After emptying thetreatment vessel into a ladle, the following chemical composition wasdetermined:

0.056 Mg I Thus, the magnesium yield amounted to 63.5 percent.

Furthermore, it is known for the carburization of iron-carbon melts toadd carbon to the surface of the bath of a melt located in an electricinduction-furnace. However, the degree of carburization with such atechnique is dependent to a large extent upon the agitation effect ofthe magnetic coils and the type of slag cover. With lower input powertothe electric furnace,

carburization together with desulfurization in the ladle, whereby therequired bath movement, on the one hand, is produced byrotation orcentrifuging or, on the other hand, by air-or gas flushing.

These known techniques exhibit the drawback that the treatment timeslast up to 10 minutes and the carbon yield is low and subjected tocertain undesired fluctuations.

It has now been additionally found that it is possible to positivelycarburize and simultaneously desulfurize and, if desired, regulate theresidual magnesium content required for the spherical graphite formationof an iron-carbon melt in a simple manner, if during the performance ofthe inventive process before and/or during the introduction of magnesiuminto the iron-carbon melt, carbon is added to the surface of the bath;The carbon is added in the form of conventional carburizing agents,preferably in the form of coke grit or sand or graphite or carbonelectrodes.

The above technique is especially suitable for the carburization of castiron, and indeed, specifically for the production of cast iron withspherical graphite.

During the production of cast iron with spherical gra-.

phite, it is necessary to reduce the sulfur content of the meltdelivered from the acidic adjusted cupola furnace and to increase thecarbon content to approximately 3.6, to 3.8 percent C.

As the treatment vessel there can advantageously be used a converter, assuch has previously been described in conjunction with FIGS. 1 and 2.

i The carbon for carburization of the melt, after filling of thestarting melt, is added to the uncovered bath in the converter which islocated in its horizontally'extending position. After the subsequentrocking or pivoting of the converter into the vertically extendingposition, the vaporizing magnesium brings about a pronounced agitationof the bath which promotes carburization. Furthermore, the stronglyreducing conditions, the basic slag, and the reduction of the sulfurcontent, act favorably for carburization. Due to the cooperation ofthese conditions, it is possible to desulfurize a melt in a singleworking operation within approximately 70 seconds to approximately 0.003percent final sulfur content, and the carbon content can be increased byapproximately 0.6 percent and the residual magnesium content can beregulated to the amount necessary for cast iron with spherical graphite.

The formation of slag in the receiving compartment and in the openingsbetween this compartment and the treatment vessel can be prevented bythe addition of small amounts of fluxing agents, such as N aCl. In sodo-.

ing, the fluxing agent is added to the pure magnesium ingots, forinstance, in a ratio of 0.2 kg NaCl/lOOO kg is shown and describedpresent' means operable from outside said vessel for closing said 1. Atiltable treatment vessel comprising means defining a melt-receivingmain chamber for said vessel, means defining a vaporizableadditive-receiving compartment fixedly secured within said vessel andincluding an additive-opening for charging said compartment withadditives from outside said vessel, means for tilting said vesselthrough approximately between a filling position and a treatmentposition, a plurality of apertures in said means defining saidcompartment to comrnunicate said compartment with said chamber, saidcompartment being arranged in at least a portion of the 7 base of saidchamber in a'manner such' that additives contained in said compartmentdo not communicate with melt contained in said chamber when said vesselis in said filling position, but said additives do communicate with saidmelt when said vessel is in said treatment position, said aperturesbeing dimensioned and arranged such that melt in said chamber passesthrough at least some of said apertures and into said compartment at apredetermined speed when said vessel is in said treatment position;

2. The vessel of claim 1, wherein said means defining said compartmentare formed of refractory material.

3. The vessel of claim 2, wherein said means defining said compartmentcomprises clay graphite plates of 10 to 50 mm thickness. Y

4. The vessel of claim 1, further including a meltopening for chargingsaid chamber with melt and a tightly fitting cover member for saidmelt-opening, said cover member including at least one throughpassageway of 10 to 50 mm.

5. The vessel of claim 1, further including stopper additive-opening. I

6. The vessel of claim 1, wherein said vessel is provided with a teacan-like pouring spout.

7. The vessel of claim 1, wherein said means defining said compartmentincludes apertures at different levels when said vessel is in saidtreatment position whereby the melt enters said compartment throughapertures located at the lower region of said compartment and can escapefrom said compartment through apertures located at the upper region ofsaid compartment.

8. The vessel of claim 7, wherein said apertures located at the lowerregion of said compartment have a diameter of 20 to 40 mm and saidapertures located at the upper region of said compartment have adiameter of 10 to 30 mm.

9. The vessel of claim 7, wherein the entire cross-sectional area ofsaid apertures located at the lower region of said compartment issmaller than the entire crosssectional area of said apertures located atthe upper region of said compartment.

10. A tiltable treatment vessel for the production of iron-carbon castmaterials with spherical graphite through the introduction ofvaporizable additives into the melt, especially pure magnesium,comprising means defining a melt-receiving main chamber for the vessel,means defining an additive-receiving compartment for the vessel, meansfor enabling tilting of such vessel between a filling position and atreatment position, said additive-receiving compartment being providedwith a plurality of openings for flow communicating saidadditive-receivingcompartment with said chamber, a first group of saidopenings providing infeed openings for permitting entry of the melt whenfilled into said main chamber into said additive-receiving compartmentfor contact with the additives contained therein to vaporize same, theremainder of said openings defining a second group of openings providingoutfeed openings for discharge of the vaporized additives and the meltcontained in said additive-receiving compartment into said main chamber,said first and second group of openings of said additive-receivingcompartment being located at different elevational positions withrespect to one another when the vessel is tilted into said treatmentposition.

11-. The treatment vessel as defined in claim 10, wherein at least aportion of said openings of said second group are upwardly directedtowards the upper 13. The treatment vessel as defined in claim 10,wherein said first group of openings are located at the lower region ofsaid additive-receiving compartment and said second group of openingsare located at the upper region of said additive-receiving compartmentwhen the vessel has been tilted into its treatment position, the totalcross-sectional area of said first group of openings equaling the totalcross-sectional area of said second group of openings.

14. The treatment vessel as defined in claim 10, I 1

wherein .said first group of openings located at the lower region ofsaid additive-receiving compartment when the vessel assumes itstreatment position possess a diameter in the range of approximately 20to 40 mm, and wherein said second group of openings located at the upperregion of the treatment compartment possess a diameter in the range ofapproximately 10 to 30 mm.

15. The treatment vessel as defined in claim 10, wherein said secondgroup of openings located at the upper region of said additive-receivingcompartment when the vessel has assumed its treatment position aredistributively arranged over at least one-third of the base surface ofthe vessel.

2. The vessel of claim 1, wherein said means defining said compartmentare formed of refractory material.
 3. The vessel of claim 2, whereinsaid means defining said compartment comprises clay graphite plates of10 to 50 mm thickness.
 4. The vessel of claim 1, further including amelt-opening for charging said chamber with melt and a tightly fittingcover member for said melt-opening, said cover member including at leastone through passageway of 10 to 50 mm.
 5. The vessel of claim 1, furtherincluding stopper means operable from outside said vessel for closingsaid additive-opening.
 6. The vessel of claim 1, wherein said vessel isprovided with a tea can-like pouring spout.
 7. The vessel of claim 1,wherein said means defining said compartment includes apertures atdifferent levels when said vessel is in said treatment position wherebythe melt enters said compartment through apertures located at the lowerregion of said compartment and can escape from said compartment throughapertures located at the upper region of said compartment.
 8. The vesselof claim 7, wherein said apertures located at the lower region of saidcompartment have a diameter of 20 to 40 mm and said apertures located atthe upper region of said compartment have a diameter of 10 to 30 mm. 9.The vessel of claim 7, wherein the entire cross-sectional area of saidapertures located at the lower region of said compartment is smallerthan the entire cross-sectional area of said apertures located at theupper region of said compartment.
 10. A tiltable treatment vessel forthe production of iron-carbon cast materials with spherical graphitethrough the introduction of vaporizable additives into the melt,especially pure magnesium, comprising means defining a melt-receivingmain chamber for the vessel, means defining an additive-receivingcompartment for the vessel, means for enabling tilting of such vesselbetween a filling position and a treatment position, saidadditive-receiving compartment being provided with a plurality ofopenings for flow communicating said additive-receiving compartment withsaid chamber, a first group of said openings providing infeed openingsfor permitting entry of the melt when filled into said main chamber intosaid additive-receiving compartment for contact with the additivescontained therein to vaporize same, the remainder of said openingsdefining a second group of openings providing outfeed openings fordischarge of the vaporized additives and the melt contained in saidadditive-receiving compartment inTo said main chamber, said first andsecond group of openings of said additive-receiving compartment beinglocated at different elevational positions with respect to one anotherwhen the vessel is tilted into said treatment position.
 11. Thetreatment vessel as defined in claim 10, wherein at least a portion ofsaid openings of said second group are upwardly directed towards theupper region of said main chamber when the vessel has been tilted intoits treatment position.
 12. The treatment vessel as defined in claim 10,wherein said first group of openings are located at the lower region ofsaid additive-receiving compartment and said second group of openings atthe upper region of said additive-receiving compartment when the vesselhas assumed its treatment position, the total cross-sectional area ofsaid first group of openings differing from the total cross-sectionalarea of said second group of openings.
 13. The treatment vessel asdefined in claim 10, wherein said first group of openings are located atthe lower region of said additive-receiving compartment and said secondgroup of openings are located at the upper region of saidadditive-receiving compartment when the vessel has been tilted into itstreatment position, the total cross-sectional area of said first groupof openings equaling the total cross-sectional area of said second groupof openings.
 14. The treatment vessel as defined in claim 10, whereinsaid first group of openings located at the lower region of saidadditive-receiving compartment when the vessel assumes its treatmentposition possess a diameter in the range of approximately 20 to 40 mm.,and wherein said second group of openings located at the upper region ofthe treatment compartment possess a diameter in the range ofapproximately 10 to 30 mm.
 15. The treatment vessel as defined in claim10, wherein said second group of openings located at the upper region ofsaid additive-receiving compartment when the vessel has assumed itstreatment position are distributively arranged over at least one-thirdof the base surface of the vessel.